RESUMEN
Os mecanismos que causam o amolecimento e a perda na textura post-mortem da carne de matrinxã foram determinados por meio das mudanças na microestrutura do músculo, imediatamente após a morte e depois de 12 horas de estocagem a -3ºC. As observações na microestrutura, realizadas com microscópio eletrônico de transmissão, foram semelhantes aos resultados obtidos na força de ruptura do músculo medidos com o texturômetro. Os valores da força da ruptura foram menores para a carne após o resfriamento. Observou-se que as fibras do colágeno do tecido conectivo pericelular se desintegraram e que as do colágeno do tecido conectivo do miocommata conservaram sua arquitetura e integridade. Houve pouca degradação da linha Z. Isso sugere que o amolecimento post-mortem da carne de mantrinxã, durante a estocagem a -3ºC, é causado pela degradação do tecido conectivo pericelular
In order to determine the mechanisms that cause the post mortem muscle softness of the matrinxã Brycon cephalus, changes in the micro structure of the muscle were observed immediately after death and after 12 hours of storage at -3º C, measuring the firmness of the flesh with test instruments. Observations by the transmission electron microscope were similar to the results obtained in the breaking strength of the muscle measured with a texturometer. The values of the breaking strength of the fish muscle were smaller after chilling. At the same time, it was observed that the collagen fibers of the pericellular connective tissue had disintegrated, while the collagen fibers of the miocommata connective tissue maintained their organization and integrity. No evident breakdown of Z-discs was observed. It is suggested that the post-mortem tenderization of the matrinxã muscle during chilled storage was due to the disintegration of the collagen fibers in the pericellular connective tissue and, in a smaller extent, to the weakening of Z-disk